A sandwich-type electrolytic suppressor comprised of two membranes of the same charge defining three channels is described in U.S. Pat. Nos. 4,999,098 or 5,352,360. The central channel is the sample flow channel while the outside flanking channels are regenerant flow channels. Current is passed between electrodes placed in each of the regenerant flow channels to facilitate generation of electrolysis ions, i.e. hydronium and hydroxide, from the water splitting reaction in the regenerant flow channels. Ion exchange screen typically of the same charge as the membrane ion exchange screens, are placed in each of the three channels. An aqueous eluent liquid stream of sample containing analyte ions to be separated of one charge, positive or negative, flows in an aqueous eluent through the sample flow channel. The electrolysis ions exchange for the eluent counter-ions to the sample analyte ions, thus converting the eluent to a suppressed (weakly ionized) form. The sample analyte counter-ions are also exchanged for electrolysis ions. For example, for anion analysis with sodium hydroxide as the eluent, the sodium ions (the sample counter-ions) are exchanged with hydronium ions thereby converting sodium hydroxide to water. In the above setup, the suppressor supplies hydronium ions at the anode which flow through the adjacent negatively charged sulfonated membrane to remove the sodium ions in the sample stream on to the cathode side. This electrolytic suppressor has directionality in terms of ion removal. In other words, the ionic movement is in one direction from the anode to the cathode for anion analysis.